The present invention relates to a power steering system that provides a steering assist force to steered road wheels of a vehicle.
In recent years, there have been proposed and developed various power steering systems. One such power steering system has, in an ECU housing that houses therein a control unit, a respiratory unit through which the air in the ECU housing can pass so as to absorb change of expansion/contraction of the air in the ECU housing (for instance, Japanese Patent Provisional Publication No. 2006-049618 (hereinafter is referred to as “JP2006-049618”)).